Screen randomly turns off or dims

Question

I have an iBook G4, and every now and again the screen randomly turns off. It doesn't respond to pressing and holding the power button, the only way I can turn it back on is by both taking out the battery and unplugging it, waiting 30 seconds, putting the battery back in and restarting it. If I put the power lead in before restarting then the display switches off almost instantly during boot up.
Other times the screen randomly dims really dark so that you can only just see outlines, in this situation it responds to pressing the power button and then enter to shut it down, and then after booting it back up it's fine ...until the next time.
The problems happen as often as every five minutes on some days and then not at all on others. Both occur when using the battery AND power lead, often (but not always) when the power cord is moved. Also I can get my power cord to flicker between green and orange if I wiggle it - not a good idea I know, I don't do it regularly
I've tried resetting the PMU with no success. Also I've tried swapping my battery and power lead with a friend, they had no problems using mine (and couldn't replicate the green-orange flickering), and I still had problems using theirs.
I read someone else's topic with suggested that the problem could be deficient soldering on the DC-In Board, so I've had a look. I'm no expert but the soldering looks ok to me, except one of the 3 metal legs connecting the actual socket bit to the board (the one which would be at the bottom under the yellow tape in http://www.macrecycling.com/images/products/922-6254.gif ) is looking a bit black and has discoloured the yellow tape black immediately on top of it. Looking at the circuit board though, this leg doesn't seem to connect to anything!
I've read numerous topics regarding similar situations and popular diagnosis include problems with:
* battery/power lead (I'm pretty confident it's not this)
* DC-In Board
* GPU
* Inverter cable
* Inverter
* Backlight
From the information I've given does anyone know what is most likely the cause?
I'm a poor student, my iBook's well past it's warranty, and I hear repairs start in the £100 region (also I've rumours the apple stores have stopped taking in iBooks for repairs now). So home repair is pretty much my only option at the moment, and any advice would be greatly appreciated.
Thanks in advance

Answer 1

I had the same trouble, but today my iBook died after draining the battery. It just drained it and it did not charged the batt while connected, also the iBook makes a small buzz sound while connected (and it does not do so while powered by the batt).
I researched and found that it is the DC board's fault, because it failed at charging while working fine on pure battery power.
i confirmed because powering up always worked perfectly while on battery power, (just as in your case).
The blackness you describe is possibly a short circuit, and you should look into it as quick as possible, before you get to a situation like mine.